In responding to the president’s desire to return Americans to the moon within his planned term of office, NASA Administrator Jim Bridenstine faces several challenges, perhaps insurmountable ones. Ignoring the political and budgetary constraints under which he must plan such a technical accomplishment, he is hampered by tired thinking going back to Apollo.Fifty-eight years ago, almost to the day, President Kennedy declared what was, at the time, a bold national goal: To send a man to the moon within a decade, and “return him safely to Earth.” The greatest challenge of Apollo was not the former, but the latter.Simply getting someone to the moon was relatively easy, even then: Launch a rocket with a crew and a lander, and land the latter on the lunar surface. It could be done with a much smaller rocket than the Saturn V.But in order to return, another vehicle would be required to first get back into orbit, and then additional propellant to get it all the way back to Earth, and that vehicle would have to be capable of entry into the atmosphere and recovery on the planet’s surface. As it turned out, two more vehicles were deployed: A lunar ...